Asymmetric racial homophily but no gender or age effects on cooperation and reputation formation in public goods dilemmas

Abstract Group heterogeneity is often thought to hinder cooperation and public goods provision, but it is unclear which differences matter most or if all diversity reduces cooperation. This study examines whether two core mechanisms of cooperation—reputation and reciprocity—operate differently in groups with varying gender, race and age compositions. Across three studies (N = 875) using the public goods game, we independently assessed how group diversity affects reputation and reciprocity in cooperative settings. Contrary to expectations, group composition (heterogeneous versus homogeneous) did not significantly alter reputation perceptions. While reciprocity differences emerged, they were due to varying leniency towards non-cooperators rather than a clear in-group bias, except in race, where White participants showed greater cooperation with similar cooperative partners over Black ones. Our findings suggest that, while similarity may influence initial group dynamics, its impact on reputation and cooperation wanes over time.